topic Re: Clean backups in Operating System - HP-UX

Clean backups

Rick Pancratz — Wed, 31 Jul 2002 18:16:55 GMT

My company is acquiring a N class system with internal storage only. If we use the MirrorDisk product, can I break the mirror at predetermined times (i.e. cron) to achieve a full and clean backup of the mirrored data?

Thanks,

Rick.

Re: Clean backups

Rodney Hills — Wed, 31 Jul 2002 18:19:44 GMT

Yes, it is a common practice.

I would halt the database server first, break the mirror, then start your database server again. That way you have a consistent state on your database.

-- Rod Hills

Re: Clean backups

A. Clay Stephenson — Wed, 31 Jul 2002 18:22:49 GMT

The answer is that it depends. You can certainly break the mirror at any time and you will get an absolutely perfect backup - at least to the extent that the backup is a perfect copy of the files at that moment in time. What is not so obvious is that this may also be a perfectly USELESS backup in that the files (e.g. database) may not have been in a consistant state when the mirror was split.
I'm trying to tell you that it depends upon your applications and that long before you choose a backup you need a plan.

I also suggest that if you are using Mirror/UX and plan to split mirrors that you have 2 mirrors so that your production environment is still mirrored while you are backing up. You really would not want a disk crash to occur while you are not mirrored. You should also examine OnlineJFS snapshot mounts as well.

Re: Clean backups

Sajid_1 — Wed, 31 Jul 2002 18:26:56 GMT

hi,

Yes you may do that. I would also recommend taking ignite backups using make_tape_recovery command.

You should be more carefull if you are going to split a database mirror for taking backups. A cold backup in this case will be better.

regds

Re: Clean backups

Rick Pancratz — Wed, 31 Jul 2002 18:33:46 GMT

Thank you all for your very helpful suggestions! I really appreciate your time.

-Rick.

Re: Clean backups

Martin Johnson — Wed, 31 Jul 2002 18:35:05 GMT

You need to insure all your data is on disk. Application, espeically DB applications, tend to buffer data in memory. Unless the buffers are flushed, the data on disk can be in an inconsistent state, making them useless in the event of a recovery.

You need to shutdown your applications to flush the buffers. There database products that will allow to dump the data in the databases without actually having to shutdown your databases. In that case, you would recover from the dumps, not the database data files.

HTH
Marty